gas-phase photocatalytic oxidation of volatile organic ... - Doria

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10 applications of air stripping in water treatment with following cleaning of air. This method of water treatment has been used to separate halogenated and non-halogenated VOCs from water (Carp et al., 2004). Photocatalytic oxidation over titanium dioxide may present a potential alternative for air treatment strategies due to its advantages such as the fact that the photocatalytic oxidation reaction proceeds effectively under ambient conditions, although higher temperatures may also be applied. 1.1 Objectives The objective of the present research was to disclose routes of chemical reactions, and estimate the kinetics and the sensitivity of gas-phase PCO towards reaction conditions in respect of air pollutants containing heteroatoms in their molecules. Deactivation of the photocatalyst and restoration of its activity was also taken under consideration to assess the practical possibility of the application of PCO to the treatment of air polluted with certain VOCs. UV-irradiated titanium dioxide, most often Degussa P25, was selected as a photocatalyst for its chemical inertness, non-toxic character and low cost. Experimental research into PCO of the following VOCs was undertaken: - methyl tert-butyl ether (MTBE) as the basic oxygenated motor fuel additive and, thus, a major non-biodegradable pollutant of groundwater; - tert-butyl alcohol (TBA) as the primary product of MTBE hydrolysis and PCO; - ethyl mercaptan (ethanethiol) as one of the reduced sulphur pungent air pollutants in the pulp-and-paper industry; - metylamine (MA) and dimethylamine (DMA) as the amino compounds often emitted by various industries. The present research had the objective of studying the gas-phase PCO of the VOCs mentioned above with a transient and a continuous flow method in simple thin-film tubular reactors. The intermediate objectives included the identification of volatile PCO products and, thus, the establishment of possible reaction pathwas, the characteristics of the reaction kinetics and examination of the catalyst life time. Thermal catalytic
11 oxidation (TCO) experiments were carried out to verify the reliability of the findings in comparison with published data available for TCO. 1.2 Air pollutants under consideration: an overview Volatile organic compounds are organic air pollutants, emitted into the atmosphere from a variety of sources, including vehicles, fossil fuel combustion, steel-making, petroleum refining, fuel refilling, industrial and residential solvent use, paint application, manufacturing of synthetic materials (plastics, carpets), food processing, agricultural activities and wood processing and burning. The most significant problem related to the emission of VOCs is the possible production of photochemical oxidants (ozone, peroxyacetyl nitrate). Tropospheric ozone, formed in the presence of sunlight from NOx and VOC emissions, creates a potential risk to public health, is damaging to crops and is involved in the formation of acid rain. Emissions of VOCs also contribute to localized pollution problems of toxicity and odor. Many VOCs take part in the depletion of the stratospheric ozone layer and may play a significant role in global warming (Manahan, 1994). The present work was focused on the air pollutant VOCs characterized below. 1.2.1 Methyl tert-butyl ether Methyl tert-butyl ether (MTBE) was the most widely used motor fuel additive in the USA until 1998 and is still the basic oxygenated additive used nowadays in the rest of the world. As a result of massive production of MTBE, significant amounts are found in groundwater because of storage tank and pipeline leaks and fuel spills (Johnson et al., 2000). Because it has a high solubility in water (about 50 g L -1 at 20 �C (Squillace et al., 1996)) and is resistant to biodegradation (Bradley et al., 1999) in ground water systems, MTBE can be present miles from the original spill (Landmeyer et al., 1998) and is expected to persist in groundwater for many years (Barker, 1998). Based on current MTBE toxicological data, a maximum drinking water level of 100 �g MTBE L -1 is suggested (Hartley et al., 1999), although this recommended advisory level does not take into
Page 1 and 2: Anna Kachina GAS-PHASE PHOTOCATALYT
Page 3 and 4: ABSTRACT Anna Kachina Gas-phase pho
Page 5: ACKNOWLEDGEMENTS 5 The author grate
Page 9 and 10: LIST OF PUBLICATIONS 7 The present
Page 11: 1 INTRODUCTION 9 Substances emitted
Page 15 and 16: 1.2.3 Amino compounds 13 The chemic
Page 17 and 18: 15 The commercialization of TiO2-ba
Page 19 and 20: 17 polymer matrix (Brezová et al.,
Page 21 and 22: 19 ambient temperatures. However, s
Page 23 and 24: 2.3 Reaction kinetics 21 The L-H mo
Page 25 and 26: 3 RESULTS AND DISCUSSION 3.1 Experi
Page 27 and 28: 3.2 Catalyst life-time and reaction
Page 29 and 30: Table 3.2.1 Catalyst deactivation t
Page 31 and 32: 29 Table 3.3.1 Reaction rate consta
Page 33 and 34: 31 Table 3.4.1 Arrhenius equation p
Page 35 and 36: References 33 Aguado, J., Grieken,
Page 37 and 38: 35 Fernández, A., Lassaletta, G.,
Page 39 and 40: 37 Lee, S. H, Kang, M., Cho, S. M.,
Page 41 and 42: 39 Sabate, J., Anderson, M. A., Agu
Page 43: 41 APPENDICES

gas-phase photocatalytic oxidation of volatile organic ... - Doria

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